feat: add unify tag (#487)

Author: tomarra

src/components/starlight/Head.astro

@@ -10,3 +10,6 @@ import Default from '@astrojs/starlight/components/Head.astro';
   is:inline
   data-domain="docs.shorebird.dev"
   src="https://plausible.io/js/script.tagged-events.js"></script>
+
+<!-- Unify Website Tag -->
+<script is:inline>!function(){var e=["identify","page","startAutoPage","stopAutoPage","startAutoIdentify","stopAutoIdentify"];function t(o){return Object.assign([],e.reduce(function(r,n){return r[n]=function(){return o.push([n,[].slice.call(arguments)]),o},r},{}))}window.unify||(window.unify=t(window.unify)),window.unifyBrowser||(window.unifyBrowser=t(window.unifyBrowser));var n=document.createElement("script");n.async=!0,n.setAttribute("src","https://tag.unifyintent.com/v1/QoBw2RtKMRTC8SgiRGVoqm/script.js"),n.setAttribute("data-api-key","wk_aZd1Wuvn_66qeweFDZsr2swVJShPAMpqiwuEv4VHm"),n.setAttribute("id","unifytag"),(document.body||document.head).appendChild(n)}();</script>